STM32F405REY7TR View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

STM32F405REY7TR

ARM Cortex-M4 32b MCU+FPU, 210DMIPS, up to 1MB Flash/192+4KB RAM, USB OTG HS/FS, Ethernet, 17 TIMs, 3 ADCs, 15 comm. interfaces & camera

STMicroelectronics 

STM32F405xx, STM32F407xx

Electrical characteristics

Equation 2

Equation 2 allows to calculate the increment step (INCSTEP):

INCSTEP = round[((215 – 1) × md × PLLN) ⁄ (100 × 5 × MODEPER)]

fVCO_OUT must be expressed in MHz.

With a modulation depth (md) = ±2 % (4 % peak to peak), and PLLN = 240 (in MHz):

INCSTEP = round[((215 – 1) × 2 × 240) ⁄ (100 × 5 × 250)] = 126md(quantitazed)%

An amplitude quantization error may be generated because the linear modulation profile is

obtained by taking the quantized values (rounded to the nearest integer) of MODPER and

INCSTEP. As a result, the achieved modulation depth is quantized. The percentage

quantized modulation depth is given by the following formula:

mdquantized% = (MODEPER × INCSTEP × 100 × 5) ⁄ ((215 – 1) × PLLN)

As a result:

mdquantized% = (250 × 126 × 100 × 5) ⁄ ((215 – 1) × 240) = 2.002%(peak)

Figure 35 and Figure 36 show the main PLL output clock waveforms in center spread and

down spread modes, where:

F0 is fPLL_OUT nominal.

Tmode is the modulation period.

md is the modulation depth.

Figure 35. PLL output clock waveforms in center spread mode

Frequency (PLL_OUT)

md

F0

md

tmode

2 x tmode

Time

ai17291

DocID022152 Rev 4

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